Dual-action displacement pump



Feb. 26, 1963 T. F. THOMPSON DUAL-ACTION DISPLACEMENT PUMP 3Sheets-Sheet 1 Filed Oct. 16, 1958 INVENTOR.

m WP w Theodore E Thompson ATTORNEYS Feb. 26, 1963 T- F. THOMPSON3,078,807

DUAL-ACTION DISPLACEMENT PUMP Filed Oct. 16, 1958 Y s Sheets-Sheet 2INVENTOR.

Theodore E Thompson ATTORNEYS Feb. 26, 1963 T. F. THOMPSON 3,078,307

DUAL-ACTION DISPLACEMENT PUMP Filed Oct. 16, 1958 s Sheets-Sheet :5

INVENTOR.

Theodore E Thompson MMH H BY ATTORNEYS United States Patent 3,078,807DUAL-ACTION DESPLACEMENT PUMP Theodore F. Thompson, Davenport, Iowa,assignor of one-half to William D. Hewit, Denver, Qolo. Filed Oct. 16,1958, Ser. No. 767,649 2 Claims. (Cl. 103126) This invention relates topumps and more particularly it relates to rotary positive displacementpumps of high capacity and high pressure.

It is an important object of the invention to provide a simplifiedrotary double displacement pump having a minimum of wear surfaces and aminimum of moving parts.

It is a further object of the invention to provide a double displacementrotary pump of high capacity and capable of producing high pressureswith a minimum expenditure of power.

It is a further object of the invention to provide a rotary displacementpump in which two interconnected rotors alternately increase anddecrease the pumping volume of interconnected chambers in which theyoperate, with a minimum of back flow and with a positive fluiddisplacement so as to provide an essentially non-pulsating pump.

It is another object of the invention to provide a rotary pump in whichat least two rotors mounted in the pump operate conjointly, rolling oneach other and each rolling on the surface of its enclosing pumpchambers with a minimum of slippage.

Another object of the invention is to provide a double rotor, a rotarypump in which the rotors are mounted on eccentric shafts so that once ineach revolution each rotor provides a complete seal from the inlet andoutlet for its enclosingchamber, and the inlet is sealed from theoutlet.

A. still further object of the invention is to provide a rotary pumpwhich includes a double rotor arrangement mounted in a housing so thatone rotor provides a seal for the opposite roller while bothsimultaneously displace liquid from the inlet to the outlet in anoverlapping discharge whereby to provide a double non-pulsatingdisplacement of fluids through the pump.

These and other objects and advantages of the invention may be readilyascertained by referring to the following description and appendeddrawings in which:

FIG. 1 is an end elevational view of a pump according to the invention;

FIG. 2 is a cross-sectional view of the pump illustrated in FIG. 1 takenalong section line 22;

FIG. 3 is a partial sectional view of the pump of the inventionillustrating one position of the pump rotors;

FIGS. 4, 5 and 6 are essentially schematic drawings. illustratingsequential steps of operation of the pump;

FIG. 7 is an end elevation of a pump of the invention illustrating thegear mounting of dual rotors of the in vention;

FIG. 8 is a cross-sectional view of one form of rotor for use in oneform ofthe pumpof the. invention;

FIG. 9 is a cross-sectional, lengthwise view through a modified rollerof the. invention; and

FIG. 10 is a cross-sectional view of a pump of the inventionillustrating a further modification thereof.

In general, the displacement pump of the invention includes a hollowhousing having two essentially cylindrical chambers of equal diameter,overlapped and interconnected in the general shape of a figure eight,with an upper and lower bight on the plane of symmetry. A roller is.provided in each chamber, with the diameter of the roller slightlysmaller than the diameter of the chamber. The rollers are; mounted oneccentric shafts which are positioned and so interconnected thatrotation of the shafts maintains the two rollers incontinuous engagementwith each other and each roller in continuous engagement with the wallof its enclosing chamber. Each roller is so proportioned as to bridgethe gap at the intersection of the two chambers, and the bridging occursalternately at degrees apart. The rollers are freely rotatably mountedon the eccentric shafts so that each roller, being in contact with thehousing, merely rolls on the inner surface of the housing and rolls oneach other. This rolling is essentially without slipping due to the factthat each roller is freely rotatable on the shaft and is not rotatablydriven. A perfectly smooth housing and roller surface is not essential,the criterion being that the surface of each roller meshes or alignswith and seals against thesurfaoe of its chamber and the surface of theopposite roller throughout each revolution. The rollers mounted on theeccentric shafts must be of such a size and the eccentricity must begreat enough to move the rollers into and out of the area of chamberoverlap to alternately increase and decrease the volume of the space ineach chamber. This increase of volume occurs alternately at the inletand the outlet at essentially 180 degrees of rotation whereby eachroller provides suction intake and pressure outlet on-a 180 degreescycle with the cycles of the rollers substantially overlapped to producea non-pulsating pumping ac tion. Since each roller is of a smallerdiameter than the chamber in which it operates, a volume or spaceremains between the roller and the surface of the chamber. The operationof the eccentric shafts is such as to move the tangential contact of therollers alternately into and out of the confines of the chambers so thatthere is an alternate in-' creasing and decreasing volume in theopposite chambers at 180 degrees apart which produces the effectivepumping action.

In the pump illustrated in FIGS. 1 through 3 for purposes of detaileddescription, a hollow housing 1 is provided with end plates 2 and 3 forenclosing intersecting cylindrical chambers 6 and 7. A foot 2a mountedon the end plate 2 and the foot 3a mounted on end plate 3 are arrangedto be attached to a base member by means of bolts or the like throughholes 4 and 5 in the feet. This arrangement provides means for anchoringthe pump in operation position. The end plates are secured to thehousing 1 by means of bolts 8 or other suitable means for securing theparts together. The joints between the housng 1 and the end plates 2 and3 must be tight to provide an essentially fluid tight connection, andfor this purpose various sealing mechanisms well known in the art may beused. Also, since this is a high pressure pump, a plurality of bolts arepreferably provided around the periphery of the chambers to provide atight enclosure capable of withstand'ng the fluid pressures which thepump is capable of producing.

A boss 10 mounted on the end plate 3' and a boss 11- mounted on the endplate 2 provide means for journaling shafts in the pump. The bosses aresubstantially of figure 8 shape extending across both chambers forsupporting the shafts. Each shaft must include a seal, and-since this isa common feature for pump shafts, no specific illustration is deemednecessary.

The cylindrical chambers 6 and 7 illustrated inthe pump intersect insuch a manner as to provide anoverlapped area, for example asillustrated in FIGURE 3,. the area oneither side of a plane 12 passingthrough the intersection of the two cylindrical chambers. A sealin'gmember 14' is mounted in the upper intersection and ex-.

tends. the length of the chambers, and a'sealng member 15 is mounted atthe lower intersection and, also, extends the length of the twocylindrical chambers. Each ofthe sealing members includes a flattenedsurface at about the intersection which is a predetermined distancebetween the intersections and in effect cuts off the point of thebightof'each intersection. The seal member 14 includes a flattened area16 while the sealing member 15 includes the flattened area 17 facing thearea 16. An upper port 20 extends through the end plate 2 above andadjacent the intersection of the cylindrical chambers and a passage 22in the housing body communicates therewith. A plurality of small bores23 extend through the sealing member 14 through the flattened area 16and interconnect the passageway 22 with the interior of the pumphousing. In a similar manner a passageway 25 in the lower portion of thehousing interconnects with the port 21 through the end plate 2 and witha plurality of bores 24 through the sealing member 15 and the area 17.One of these passages provides an inlet for the pump while the oppositepassageway provides an outlet, depending on the rotation of the rotorsin the pump.

A shaft is journaled for rotation concentrically with the chamber 6, anda shaft 31 is journaled concentrically in chamber 7. An eccentric member32 is mounted on the shaft 30 for conjoint rotation therewith, and aneccentric member 33 is rigidly mounted on the shaft 31 for conjointrotation therewith. The shafts 30 and 31 are geared together, by meansof gears 35 and 36 mounted on the ends of the shafts which extendthrough the boss 11. The shafts rotate in opposite directions and mustbe so geared together with a minimum of play and the eccentrics must besecurely fastened to the shafts so that the zenith of each of theeccentrics is exactly 180 de ees of rotation apart. Furthermore, theshafts are so geared together by spur gears 35 and 36, FIG. 7, that theyrotate in opposite directions at substantially the same speed. Acylindrical rotor 40 is freely, rotatably mounted on the eccentric 32,and a cylindrical rotor 41 is freely, rotatably mounted on the eccentric33. Each rotor is essentially the same length as the housing 1 so thatthe ends of the rotors seal against the end plates 2 and 3 of the pump.

One form of the rotor is illustrated in FIG. 8 wherein the cylindricalrotor body 44, which is normally made of a rigid material such as steelor the like, is mounted on roller bearings 45 on the eccentric 32. Thismounting permits the member 44 to freely rotate on the eccentric. Theresilient covering 46 is bonded or otherwise secured to the exteriorsurface of the cylindrical member 44 forming a covering or sheath on theroller. The parts are dimensioned so that the exterior surface of theresilient material 46 is in contact and slightly compressed on the innersurface of the cylindrical chamber 6. The free rotation of the rotor onthe eccentric permits it to roll on the surface essentially withoutslipping. In a similar manner, the opposite rotor is in contact with thesurface of the chamber 7. The two rotors are in contact and they arecompressed so that the two cylinders ride on one another alsoessentially without slipping and without slippage on the chamber walls.The resilient material covering the roller is slightly compressible atits contact points, and under normal operating conditions there is onlyan insignificant leakage at such contact points. The compression, also,provides a right frictional engagement between the rotor members whichprevents back-leaking from outlet to inlet.

The shaft 30 extends through the boss 11 and provides means for mountinga pulley for driving the pump, including a key way 50 cut in the shaft.Suitable packing and bearings must, of course, be provided to preventfluid leaking and to provide efiicient rotation. Such packing andbearing assemblies may be essentially known types.

The diameter of each rotor is slightly less than the diameter of thechamber in which it is mounted so that there is a space or a volumebetween the exterior surface of the rotor and the surface of thechamber. This volume represents the volume of displaced liquid movedfrom the inlet to the outlet of the pump. As explained below, theoperation of the pump provides a positive displacement of the fluid fromthe inlet to the outlet. Both rotors provide the pumping action so thepump, as illustrated, has a dual displacement of fluid for eachrevolution.

In one very effective size, a pump is provided in which the chambershave 3.89 inch diameter, and the axes of the cylinders are mounted3.4687 inches apart. This provides an overlap area between the cylindersso that there is in effect a figure 8 chamber in the pump. Thecylindrical chambers are provided with parallel axes. The bight at theintersection of the cylinders is fitted with a seal member, as explainedabove, and bores through the sealing members provide the inlet and theoutlet openings for the pump. The housing is 2.27 inches in Width,however, the length or the width of the housing may be varied as thismeasurement determines the capacity of the same diameter pumps. A 0.669inch shaft is journaled for concentric rotation in each chamber and aone and a quarter inch diameter member is mounted 0.215 inch off centeror concentricity forming the eccentric member on the shaft. Thisprovides a throw of 0.215 inch for each rotor. A 3.520 inch externaldiameter roller or rotor is mounted on roller bearings mounted on eacheccentric. The roller is covered with a soft durometer rubber sheathwhich permits the rollers to be squeezed against the surfaces andagainst each other. The compression of the rubber sheath is aboutone-thirty-second of an inch on each side. With the pumps of thisdimension and with the shafts operating at about 600 r.p.m. the pumpdelivers five gallons per minute at about 900 lbs. pressure. Higherpressure and capacity may be achieved by increasing the pump speed.

The operation of the pump is more readily understood by referring toFIGS. 3 through 6 which illustrate various positions of the rollersduring movement. It is essential in the consideration of the operationof the pump to note that each eccentric rotates freely in the rollers,and the rollers merely roll around the inner surfaces of the chambersand roll against each other essentially without lost motion between therollers or between the housing or casing. In FIG. 3 the rollers areshown in the extreme left position or nine oclock position where theroller 41 is contacting the housing. In this position the roller 40 isalso in the nine oclock position tangentially contacting roller 41. Thisleaves a maximum space between the housing and the roller 40. Also, inthis position the roller 40 contacts both sealing member 15 and sealingmember 14 completely sealing chamber 6 from the inlet and outlet ports.Rotor 41 on the other hand is not in contact with either sealing member.According to the rotation of the shafts as indicated by the arrows,sealing member 14 is the inlet and the other sealing member 15 is theoutlet. In this position the space in chamber 7 adjacent to inlet isincreasing in size while the space adjacent to the outlet 15 in thechamber 7 is decreasing.

In the position illustrated in FIG. 4, the shafts have turned 45 degreesin the indicated direction and the rollers also have moved essentially45 degrees. In this position the roller 40 is still substantially incontact with the inlet sealing member 14, but it is no longer in contactwith sealing member 15. The volume between the roller 40 and the casingchamber 6 has been opened to the outlet 15. As the roller 41 has moved45 degrees downwardly the volume in this chamber adjacent to the outlethas been decreased, thus forcing the liquid out the outlet.Simultaneously, the roller 40 has moved up providing communication forthe space in chamber 6 with the outlet. Since that roller 40 has movedaround 45 degrees, the space in chamber 6 has been decreased and thepressure created by decreasing volume is now released through the outlet15. It is to be noted that the roller 41 was discharging continuouslywhile at some point in the 45 degrees rotation, the movement of roller40 opened the outlet to the volume of roller 40 providing in effect acontinuous discharge without pulsation. Simultaneously with the actionat the discharge, the inlet volume of chamber 7 has increased due to themovement of the roller 41, thereby increasing the suction on the inletand drawing in more fluid. Since the roller 40 is essentially still incontact with the sealing member 14 during this rotation. The movement ofthe roller is essentially all discharge.

Further rotation of the shafts, to the position illustated in FIG. 5,where the zenith of the eccentric 33 is vertically downward and thezenith of the eccentric 32 is vertically upward, moves the rollers to aposition where the inlet olume ofroller 41 and minor inlet v um of 40substantially equals the outlet volume of roller 40 and the small outletvolume of roller 41. In this position'the tangentialcontact between thetwo rollers is substantially along the Plane of symmetry llthrough thechambers. Also, in this position the roller 40 is now o of .wntact withthe s alina ember 14 h inlet volume of roller 40 is increasing therebycausing a suction while the inlet volume of roller 41 is approachingmaximum due to the movement of the roller 41 upwardly towards thesealing member 14. The roller 40 is displacing liquid from the space inthe chamber toward the outlet 15, and the roller 41 is completing itsdischarge.

Further movement of the shafts causes a displacement movement of therollers to the position indicated in FIG. 6, where the rotor 41 is nowin sealing contact with the outlet sealing member 15 and the inletvolume of the chamber 7 is approaching maximum volume. Simultaneouslythe discharge volume of chamber 6 is decreasing, displacing the fluidthrough the outlet sealing member 15. It is to be noted in this positionthat the rotor 41 has extended to right past the plane of symmetry 12 sothat the volume in chamber 6 is approaching its minimum while the volumein chamber 7 is approaching a maximum. Continued rotation of the shaftswill move the rotor 41 to the position where it contacts both thesealing members 14 and 15, completely sealing the chamber 7 from boththe inlet and the outlet opening, which is exactly 180 degrees fromposition as illustrated in FIG. 3. In this position the volume inchamber 7 is at a maximum while the volume in chamber 6 is at a minimum.Further rotation of the shafts continues the displacement of the fluidat the outlet volume from chamber 6 and before it is completelydischarged the space of chamber 7 opens up to the outlet forming acontinuous discharge. Simultaneously, the inlet volume of chamber 6opens up prior to the closing of the inlet of 7 forming a continuousinlet.

A modified roller is illustrated in FIG. 9 wherein a roller body 50 isarranged for mounting on the bearing set mounted on the eccentric of theshafts, and the body of the roller 50 is slightly smaller than the widthof the housing so that the roller body does not contact the end platesof the pump. A resilient sheath 52 is sealed to the exterior surface ofthe body 50 and the diameter of the resilient body is slightly largerthan the theoretical diameter of the rollers if they exactly fit thehousing. This is essentially the same arrangement as the rollersdescribed in FIG. 8 to provide the compression between each roller andits housing and roller on roller to prevent back-leaking of fluid. Ametal disc insert 53 is sealed in the rubber with a bearing surface 54in position to contact the end plates of the pump. The disc 53 may be asteel member having a hardened face 54 or it may be a hardened steelmember providing a wearing surface for the roller against the endplates. The wearing face 54 of the disc 53 extends slightly beyond thedisc surface 55 forming a shallow recess 56 which may act as a greasering for holding a body of lubricating grease. The grease also acts as aseal against the end plates of the pump. With the use of the seal ring53 the distance between the bearing face 54 on the one end and theopposite bearing face on the other seal ring on the other end of theroller may be made slightly larger than the distance between the endplates of the pump, thereby causing the resilient covering to exert aspring like pressure on the disc against the end plate forming a tightseal to prevent 6 leaking andback flow of fluid from the pressure sideof the pump.

In the modification illustrated in FIG. 10, a housing 1 is provided withend plates 60 and 61. The endplate 60 is provided with a foot 60a, andthe end plate 61 is provided with its foot 61a for securing the pump toa base member. In this instance the end plate .60 includes an enclosedboss 63 having a bearing cavity 64 therein for journaling a shaft 65therein by means of roller bearings 66. The end plate 60 includes twosuch bosses, one for each shaft, providing a sealed bearing for eachshaft and thereby reducing the possibility of leakage. A.boss isprovided for the opposite ends of the shafts in end plate 61 to providea gear mount for both shafts and a drive end 68 on the shaft 65. Gears69 are mounted on the shafts to provide conjoint rotation and theshafts, as explained above. The shaft 68 may be provided with a key way70 for keying a drive pulley thereto.

An additional modification is provided in that the inlet isinterconnected with a passage 76 which extends through the housing 1essentially in the bight between the two chambers. Instead ofcommunicating with bores (as shown in FIG. 2) through the sealingprojections 77 and 88 of housing 1, a bypass or passage way around eachof the sealing members is provided. Thus a passage 78 in end plate 60and a similar passage 79 in end plate 61 provides an inlet. The passages78 and 79 communicate with the pump interior adjacent to the sealingmember 77 and when either roller is in sealing position against thesealing member 77 either or both of the inlet or outlet passages arecompletely closed from the space in the chamber. In a similar manner anoutlet 80 communicates with a passage way 81 in the housing 1. A passage82 in the end plate 60 and a passage 83 in end plate 61 providecommunication with the interior of the pump around a sealing member 88.In this manner the inlet end outlet is provided for the pump withoutrequiring the small bores through the sealing members as illustrated forthe sealing members 14 and 15. Such passage ways around the sealingmembers are satisfactory for short length cylindrical pumps, but as thecylindrical rollers and chambers are elongated it is preferable to havethe communication through the sealing member. This provides for auniform pressure along the length of the rotor, and a greater volume maybe passed.

While the invention has been illustrated by reference to specificembodiments, there is no intent to limit the scope or concept to theprecise details so set forth, except as defined in the following claims.

I claim:

1. In a positive displacement pump having a housing including a pair ofhollow cylindrical chambers of the same diameter partially overlappingalong a chord which is substantially less than the maximum diameter ofsaid chambers, and a pair of end walls enclosing the chambers, theimprovement which comprises, a rigid cylindrical roller substantiallysmaller in diameter than its enclosing chamber mounted in each chamber,a shaft concentrically mounted through each chamber, a cylindricalmember eccentrically and rigidly secured to each said shaft, a bearingset mounted on each said cylindrical member, one of said rollers mountedon each bearing set so as to be freely rotatable thereon, a resilientmaterial covering of substantial thickness secured to the periphery ofeach roller, the peripheral diameter of each resilient covering beingless than the diameter of the chambers but great enough for one coveringto contact both wall ends at the intersection of the chambers and bearagainst the other roller which is bearing against its chambers wall at apoint of intersection of a line through both shafts and the chamberwall, a sealing member mounted at each intersection of the chamberswalls and positioned to seal the resilient covering when the covering isbearing against it, each sealing member including a planar surfaceperpendicular to a plane through the intersection of the chambers andthe edges of said surfaces providing the seal for each roller, inletmeans including a plurality of small bores extending from end wall toend Wall across one said surface, outlet means including a plurality ofsmall bores extending from end wall to end wall across the other saidsurface, a circular gear mounted on each shaft protruding beyond theside wall of the chamber and intermeshed together for conjoint rotationof said shafts, and means for rotating at least one of said shafts.

2. A positive displacement pump according to claim 11 in which each ofsaid small bores of each of said inlet and outlet extends through theseal means and cornmunicates with an inlet and outlet passageway in thepump housing respectively.

References Cited in the file of this patent UNITED STATES PATENTS HollyJuly 6, Schmidt July 29, Jaworowski Dec. 22, Lindberg Dec. 28, BrownJan. 19, Barker Oct. 19,

FOREIGN PATENTS Germany Feb. 19, Germany Oct. 28, Germany Feb. 8,Germany Sept. 21,

1. IN A POSITIVE DISPLACEMENT PUMP HAVING A HOUSING INCLUDING A PAIR OFHOLLOW CYLINDRICAL CHAMBERS OF THE SAME DIAMETER PARTIALLY OVERLAPPINGALONG A CHORD WHICH IS SUBSTANTIALLY LESS THAN THE MAXIMUM DIAMETER OFSAID CHAMBERS, AND A PAIR OF END WALLS ENCLOSING THE CHAMBERS, THEIMPROVEMENT WHICH COMPRISES, A RIGID CYLINDRICAL ROLLER SUBSTANTIALLYSMALLER IN DIAMETER THAN ITS ENCLOSING CHAMBER MOUNTED IN EACH CHAMBER,A SHAFT CONCENTRICALLY MOUNTED THROUGH EACH CHAMBER, A CYLINDRICALMEMBER ECCENTRICALLY AND RIGIDLY SECURED TO EACH SAID SHAFT, A BEARINGSET MOUNTED ON EACH SAID CYLINDRICAL MEMBER, ONE OF SAID ROLLERS MOUNTEDON EACH BEARING SET SO TO BE FREELY ROTATABLE THEREON, A RESILIENTMATERIAL COVERING OF SUBSTANTIAL THICKNESS SECURED TO THE PERIPHERY OFEACH ROLLER, THE PERIPHERAL DIAMETER OF EACH RESILIENT COVERING BEINGLESS THAN THE DIAMETER OF THE CHAMBERS BUT GREAT ENOUGH FOR ONE COVERINGTO CONTACT BOTH WALL ENDS AT THE INTERSECTION OF THE CHAMBERS AND BEARAGAINST THE OTHER ROLLER WHICH IS BEARING AGAINST ITS CHAMBER''S WALL ATA POINT OF INTERSECTION OF A LINE THROUGH BOTH SHAFTS AND THE CHAMBERWALL, A SEALING MEMBER MOUNTED AT EACH INTERSECTION OF THE CHAMBERSWALLS AND POSITIONED TO SEAL THE RESILIENT COVERING WHEN THE COVERING ISBEARING AGAINST IT, EACH SEALING MEMBER INCLUDING A PLANAR SURFACEPERPENDICULAR TO A PLANE THROUGH THE INTERSECTION OF THE CHAMBERS ANDTHE EDGES OF SAID SURFACES PROVIDING THE SEAL FOR EACH ROLLER, INLETMEANS INCLUDING A PLURALITY OF SMALL BORES EXTENDING FROM END WALL TOEND WALL ACROSS ONE SAID SURFACE, OUTLET MEANS INCLUDING A PLURALITY OFSMALL BORES EXTENDING FROM END WALL TO END WALL ACROSS THE OTHER SAIDSURFACE, A CIRCULAR GEAR MOUNTED ON EACH SHAFT PROTRUDING BEYOND THESIDE WALL OF THE CHAMBER AND INTERMESHED TOGETHER FOR CONJOINT ROTATIONOF SAID SHAFTS, AND MEANS FOR ROTATING AT LEAST ONE OF SAID SHAFTS.